Tube bending die with flowable rubber pad to prevent collapse of the tube



Aug. 25, 1959 H. TEITELMAN TUBE BENDING DIE WITH FLOWABLE RUBBER PAD TOPREVENT COLLAPSE OF THE TUBE Filed Sept. 24, 1954 IN V EN TOR.

l a! 72/2154 MAN 14 T TOIPNE Y5 BYWMMJ United States Patent TUBE BENDINGDIE WITH FLOWABLE RUBBER PAD TO PREVENT COLLAPSE OF THE TUBE HerbertTeitelman, Waban, Mass.

Application September 24, 1954, Serial No. 458,293

9 Claims. (Cl. 153-48) (Granted under Title 35, US. Code (1952), sec.266) The invention described herein may be manufactured and used by orfor the Government of the United States of America for governmentalpurposes without the payment of any royalties thereon or therefor.

The present invention concerns a die and in particular concerns a pipebending die having a resilient face.

It has been the practice in the past in bending pipe to provide a maledie that along its bending edge is machined with precision. It has beencustomary to form such dies ofhigh quality steel.

One disadvantage of precision machined steel dies has been that thesedies are exceedingly expensive because of the time and high costinvolved in the precision machining of the bending face. Likewise thereis loss of time in the pipe bending operation while awaiting manufactureof the precision machined die which manufacture involves the expenditureof a large amount of time.

A further disadvantage resides in the fact that once the precisionmachining operation has been performed, the metal die can bend only oneradius of pipe and it is impossible with such a die to bend more thanone radius. Furthermore, because of springback in the pipe that is bentit is necessary that compensations for such springback be made; theradius of the precision machine die is therefore carefully calculated toa smaller radius than the radius of the pipe following the springback.In order to bend different pipes to different radii, it is necessary toprovide a plurality of dies of the proper radii.

The present invention overcomes these difficulties by providing a metaldie having a resilient pad that forms the bending face. It isunnecessary to perform a precision machining operation and this reducesthe time involved in making the die and also the cost of manufacture.Likewise, the die can easily be modified in a matter of minutes to benda variety of different pipe radii by simply providing rubber shimsappropriately at the center or ends or both of the bending surface.

Furthermore, it is a simple matter to compensate with the rubber faceddie for the springback inherent in the pipe to be bent.

Further advantages in use of the die having the rubber bending surfacearise from the fact that both the rubber and the material of the pipebeing bent actually flow during bending which reduces gathers on theinside of the pipe bend and likewise reduces thinning and flatten ing onthe outside of the pipe bend.

An object of the invention is to provide a die.

Another object is to provide a pipe bending die having a resilientbending face.

Another object is to provide a pipe bending die having a rubber bendingface.

Another object is to provide a pipe bending die that is inexpensive tomanufacture, that involves a minimum of time during manufacture, andthat completely eliminates the need for precision machining.

O ther objects and many of the attendant advantages of this inventionwill be readily appreciated as the same ice 2 becomes better understoodby reference to the following detailed description when considered inconnection with the accompanying drawings wherein:

Fig. 1 is a perspective view of a preferred embodiment of the invention,

Fig. 2 is a top plan view of the preferred embodiment,

Fig. 3 is an end elevation of Fig. 2,

Fig. 4 is a vertical sectional View taken on lines 44 of Fig. 2 omittingcertain parts and in addition showing the diein operation, and v Fig. 5is a view of shim for varying the curvature of the die. 7 p

In the drawings there is shown a pipe bending die 10 comprising a topplate 11 and a bottom plate 12 which are separated by a spacer 13extending completely along the substantially straight rear edges ofplates 11, 12. The forward edges 11a, 12a of plates 11, 12 are arcuate.Top plate '11, bottom plate 12 and spacer 13 are welded together to forman integral unit and blocks 14, 15 are welded across the sides of topplates 11, 12 to partly close the space formed between plates 11, 12. Anopening 16 is formed centrally at the rear of spacer 13 to accommodate afitting for mounting the die 10 in a pipe bending machine 17, one typeof which is shown in US. Patent No. 2,382,266 issued to G. N. Simonsenon August 14, 1945.

The space formed between plates -11, 12 is substantially filled by "arubber pad 18 having an arcuate bending sur face 19. Top plate 11together with bottom plate 12 and rubber pad 18 are formed with theirforward edges arcuate and with the forward edges of top plate 11 andbottom plate 12 slightly overhanging the arcuate bending surface 19 ofpad 18 to form a convex groove the bottom of which is defined by bendingsurface '19 of pad .18.

The arcuate forward edges of top plate 11 and bottom plate 12 are roughcut and it is unnecessary that they be precision machined. As shown inthe preferred embodiment the arcuate forward edges of top plate 11 andbottom plate 12 together with bending surface 19 of pad 18 cover an arcof less than of about 10 inch radius. Obviously the die can be made tocover an are 90 or larger and a radius that is larger or smaller than 10inches.

Bolts 22 and 23 extend upwardly from bottom plate 12 through rubber pad18 and top plate 12. Nuts 24, 25 are tightened in such manner that thespacing of forward arcuate edges 11a, 12a of plates 11, 12 is maintainedconstant under all conditions of stress.

Footpads 31, 32 are provided on bottom plate 12 and footpads 33, 34 areprovided on top plate 11. In operation, the die can be inverted from theposition shown in Fig. 1 and rest upon footpads 33, 34. Such inversionin use provides uniform wear and preserves the length of the die.

In operation the die is mounted upon a suitable machine with a pipe 21to be bent in front of rubber bending surface 19 with the ends of thepipe at each side of the die being restrained. The die is moved forwardtoward the observer as seen in Fig. 1, to cause bending of the pipe.

Due to the rigid mounting of top plate 11 with respect to bottom plate12, it is thought impossible for the rubber to flow in an up and downdirection as seen in Fig. 1' but during the bending operation when thepipe 21 is bent over the resilient fiowable rubber convex die thepressure of the pipe on the rubber will result in an indentation of thepipe laterally of itself into the rubber, with some of the rubber alongthe sides of the indentation deformed outwardly along the sides of thepipe as shown in Fig. 4

able or flowable when displaced by its deformation resulting from therubber pressing against the pipe. It is thought that because of the flowof rubber along exposed bending surface or face 19 and because of theuniform flow of metal in the pipe being bent, the outside of the pipeduring bending undergoes uniform flow of metal; it is definitelyestablished that there is uniform thinning of the outer surface of thebent pipe which completely elimia smaller radius is provided. Similarlyby use of suitable shims compensation is easily provided for springbackof the pipe after being bent regardless of the degree the particularpipe springs back.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

I claim:

1. A pipe bending die comprising a casing having a chamber therein withan open edge and otherwise closed, and a body of elastic andincompressible but deformable material confined snugly in said chamberand having its exposed surface at said open edge of the chamber ofconvexly arcuate shape corresponding to the curvature of a bend to beplaced in said pipe, and over which a pipe may be bent when the part ofthe pipe to be bent is disposed lengthwise of itself along the curvatureof said arcuate surface, whereby the pipe when said arcuate surface ispressed against it will indent itself somewhat into said body anddisplace by deformation some of the elastic body sidewise up along thesides of the pipe where it resists sidewise deformation of the pipe atthe bend during the bending.

2. A pipe bending die comprising a flat top plate having a convexlyarcuate forward edge, a back edge, and end edges, a flat bottom platehaving the same configuration as the top plate disposed in spacedrelation from the top plate and in registration therewith, a spacerextending between the top plate and the bottom plate along the back andend edges thereof and integral therewith, said plates and spacerdefining a space therebetween open solely along said arcuate edge, and aresilient rubber pad confined in said space and having a substantiallystraight back edge resting against the forward edge of said spacer, saidpad of elastic, incompressible but deformable material having a convexlyarcuate exposed forward surface over which a pipe may be bent, wherebythe pipe will be indented into the pad and displace by deformation someof the elastic material sidewise up along the sides of the pipe where itresists sidewise deformation of the pipe at the bend during the bending.

3. A pipe bending die comprising a flat top plate having a substantiallystraight rear end and a convexly arcuate forward edge, a flat bottomplate having the same configuration as the top plate disposed in spacedrelation from the top plate and in registration therewith, a spacerplate extending between the top plate and the bottom plate along theback edges thereof and united therewith, said plates and spacer defininga space there between, a pair of end blocks extending across part of thespace one block at each side of said plates, a resilient rubber padconfined in said space and having a substantially straight back edgeresting against the forward edge of said spacer, said pad having aconvexly arcuate exposed forward edge opposite from said straight backedge and over which pipes may be bent, a pair of bolts extendingupwardly from said bottom plate through said pad and top plate, andapair of nuts one on each of said bolts, to lock said top plate and saidbottom plate against spreading when the rubber between the plates iscompressed by bending a pipe thereover.

4. A pipe bending die comprising a fiat top plate having a substantiallystraight rear end and a convexly arcuate forward edge, a flat bottomplate having the same configuration as the top plate disposed in spacedrelation from the top plate and in registration therewith, a spacerextending between the top plate and the bottom plate along the bacl;edges thereof and united therewith, said plates and spacer defining aspace there between open along the arcuate forward edge, a pair of endblocks extending across and partially closing part of the space, oneblock at each side of said plates, and a resilient rubber pad confinedin said space and having a substantially straight back edge restingagainst the forward edge of said spacer, said pad having an exposedconvexly arcuate forward edge over which a pipe may be mechanicallybent.

5. A pipe bending die comprising a flat top plate having a substantiallystraight rear end and a convexly arcuate forward edge, a flat bottomplate having a similar configuration as the top plate disposed in spacedrelation from the top plate and in registration therewith, a spacerextending between the top plate and the bottom plate along the backedges thereof and integral therewith, said plates and spacer defining aspace there between, a pair of end blocks extending across part of thespace one block at each end of said plates, and a resilient rubber paddis posed in and filling said space and having substantially straightback edge resting against the forward edge of said spacer and abuttingthe end blocks, said pad having an exposed, convexly arcuate forwardedge, said pad being arranged with the forward edges of said top plateand said bottom plate slightly overhanging the forward edge of said padto provide a convex groove the bottom of which is formed by the forwardedge of said pad.

6. A pipe bending die comprising a flat top plate having a substantiallystraight rear end and a convexly arcuate forward edge, a flat bottomplate having a similar configuration as the top plate, disposed inspaced relation from the top plate and in registration therewith, aspacer extending between the top plate and the bottom plate along theback edges thereof and integral therewith, said plates and spacerdefining a space there between, a pair of end blocks extending acrosspart of the space one block at each side of said plates, a resilientrubber pad disposed in and largely filling said space and having asubstantially straight back edge resting against the forward edge ofsaid spacer and ends abutting said blocks, said pad having an exposed,convexly arcuate forward edge, said pad being arranged with the forwardedges of said top plate and said bottom plate slightly overhanging theforward edge of said pad to provide a convex groove the bottom of whichis formed by the forward edge of said pad, a pair of bolts extendingupwardly from said bottom plate through saidipad and top plate, and apair of nuts one on each of said bolts, to lock said top plate and saidbottom plate against spreading.

7. A device for use in bending hollow pipe about an axis that extendslaterally of the pipe length, which comprises a form having therein acavity with an open face and otherwise closed, an elastic body havingthe properties of elastic flowable rubber confined in said cavity with apipe bending face exposed through said open form face, said elastic bodyhaving its said exposed face convexly arcuate and of a curvature alongthe are approximately equal to that desired to be formed in said hollowpipe that is bent thereover, whereby when said arcuate bending face ofsaid body is disposed lengthwise along a hollow pipe and pressedthereagainst with a force sufiicient to bend the pipe to conform to saidconvex curvature, the exposed face of said elastic body will be indentedby said pipe and flow somewhat along the transverse periphery of thepipe and resist flattening of the pipe at the arcuate bend placedtherein.

8. The device as set forth in claim 7, wherein the opposite sides ofsaid form which define the sides of the open face of said cavity extenda substantial distance outwardly beyond and clear of the arcuate face ofsaid elastic body, suflicient, when the arcuate bending face of saidelastic body is indented by a pipe being bent thereover, to aid inpressing the deformed body along the indentation against the sides ofthe pipe at the bend.

9. The method of bending a tubular pipe of bendable material, while thepipe at the bend retains its original cross-sectional shape, whichcomprises pressing against that portion of the pipe where a bend is tobe formed an exposed =arcuate convex surface of an otherwise confinedbody of elastic, incompressible, but deformable material, with the pipeextending lengthwise of itself along said arcuate surface and withsufficient force to cause said pipe to conform to the curvature of saidarcuate surface, whereby the pressure of the arcuate surface of saidelastic body against said pipe will indent the pipe into said body anddisplace by. deformation some of the elastic body up along the sides ofthe pipe and resist sidewise deformation of the pipe at the bend duringthe bending.

References Cited in the file of this patent UNITED STATES PATENTS447,295 Brenner Mar. 3, 1891 1,267,591 Rehbein May 28, 1918 1,268,360Kimball June 4, 1918 1,743,100 Blackburn Jan. 14, 1930 2,055,077 GuerinSept. 22, 1936 2,303,059 Misfeldt Nov. 24, 1942 2,382,266 Simonsen Aug.14, 1945 2,397,608 Johnson Apr. 2, 1946 2,799,317 Toulmin July 16, 1957FOREIGN PATENTS 1,743,100 Great Britain Jan. 14, 1930 417,656 GreatBritain Oct. 3, 1934

